This protocol enabled the procurement of fasting human plasma for isolation of lipoproteins. The cellular effects and chemistry of modified lipoproteins - both oxidized and aggregated - were studied. Oxidized low density lipoproteins (oxLDL) were known to be toxic to a variety of cell types, but relatively little was known about the toxic effects of oxLDL on vascular smooth muscle cells (SMC). We found that LDL oxidized by incubation with 5 fM cupric ions was toxic to cultured porcine SMC when administered at concentrations of 25 fg protein/ml and higher. The toxicity was demonstrated whether cells were proliferating or not, and was most evident in the presence of 0.4% lipoprotein-deficient serum - characteristics distinct from the toxicity of iron-oxidized LDL for cultured fibroblasts. Inhibition of a-hydroxy-a-methylglutaryl CoA reductase was hypothesized as a mechanism of toxicity, but mevalonic acid, the product of this enzyme, failed to protect against the toxicity of either oxLDL or the pure oxysterols. Alpha-tocopherol, alpha-tocopherol acetate, probucol, butylated hydroxytoluene, and deferoxamine provided partial protection to SMC exposed to oxLDL. These results suggested a role for newly initiated lipid peroxidation in the development of toxicity. Results were published in Atherosclerosis.